Magnetic speedometer



A. C. WOOD. MAGNETIC SPEEDOMETER. APPLICATlON FILED 0011s, 1920.

Patented m 13 m1,

1,400,19&

[NVENTOR 0%16777411/ 6. Wood WW 15' A TTORNEY S UNITED STATE-S PATENT OFFICE.

ANDREW C. WOOD, OF CHICAGO, ILLINOIS, ASSIG-NOR TO STEWART-WARNER SPEEDOMETER CORPORATION, OF CHICAGO, ILLINOIS, A CORPORATION OF VIRGINIA.

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Specification of Letters Patent.

Patented Dec. 13, 1921.

Application filed October 16, 1920. Serial No. 417,449.

' T all whom it may concern Cook and the State of'Illinois, have invented,

certain new and useful Improvements in Magnetic Speedometers, of which the following is a specification, reference being had to the accompanying drawings, forming a part thereof.

The purpose of this inventlon 15 to ,provide an improved construction of-magnetic speedometer, particularly with reference to the means of compensating for temperature change and calibration. It consists in the elements and features of constructlon shown and described as indicated in the claims.

In the drawings: 7

Figure 1 is a section of a portion of an instrument embodying this invention, section being made axially with respect to the speedometer rotor.

Fig. 2 is a front elevation of the rotor and parts carried thereby.

Fig. 3 is a detail elevation looking in the direction of the arrow III, on Fig. 2, of the field deflector and its securing and adjusting screw and supporting bracket.

Fig. 1 is a plan View of a blank from which the bracket for carrying the field deflector is made.

Fig. 5 is an end view of said bracket showing the manner in which it is produced on said blank.

Fig. 6 is a view similar to Fig.2, showing a modification.

Fig. 7 is a view similar to Fig. 3, showing a modification in respect to another detail.

As to its general construction in respect to the mounting and driving of the magnet, and in respect to the mounting of the oscillating drive member, the instrument shown in the drawings is substantially similar to that which is shown and described as to these features in my co-pending application, Serial No. 417,448, filed October 15, 1920 and this general construction of these parts will require no more description here than necessary to identify them. This construction. is as follows:

The casing, A, ha a mount, A axially apertured and having mounted at a distance apart along its said axial aperture two ball bearings, 2, 2, for the shaft, 3, of the rotor, 4:, said shaft being axially hollow from end to end to accommodate the spindle, 6, of a non-magnetic drag member, 7, said spindle extending through the rotor shaft to reach a step bearing at 8, said bearing being mounted in a cover plate 9, which closes a recess, 10, which constitutes an enlargement or counterbore around the axial aperture of the mount, A for admitting the rear ball bear ing, 2, and accommodating the compensating or adjustment member thereof, 2*. The rotor shaft has, situated between the ball bearings, and preferably integral with it, a gear, 11, and the mount, A has a transverse aperture, a which opens laterally into the axial aperture, a, in which transverse aperture the drive shaft, 12, extends and carries a worm or the like driving gear member, 13, for meshing with the gear, 11, on the drive shaft. The front plate, 15, of the casing has struck up from it a bracket arm, 15, for carrying the upper or forward bearing, 15", of the spindle, 6, which extends out through said bearing-and also through a dial plate, 17, for carrying the index hand, 18. The bracket arm, 15*, serves also for affording securement for the outer end of the biasing hair spring, 20, preferably of non-magnetic material as bronze, not liable to become magnetized by the presence of the magnet whose inner end is secured to the spindle, 6, for biasing the drag member as to rotation in one direction to a normal or zero position of the index finger, 18, on the dial, 17 The drag member, 7 is of cup form having its web or bottom substantially parallel with the plane of rotation of the magnet and laterally adjacent thereto, and its cup wall or flange encompassing the magnet path quite proximate to the outer circumference of the magnet.

25 is the field deflecting member and for that purpose preferably made of soft iron. It is a fiat bar arcuate in form extending through at least ninety degrees conformed approximately to the path of rotation of the magnet, and mounted with one end free for movement positioned opposite the interpolar gap of the magnet. The other end somewhat more than ninety degrees around from the said free end is bent at a right angle to extend across the plane of rotation of the magnet, said transversely-extending terminal portion, 25, affording means for mounting the field deflector upon the rotor, which is further accomplished by means of a bracket, 26, secured at one end to the rotor near the shaft, extending out therefrom past the inthe calibrating ad ustment has been made ner side of the magnet and bent at a right angle to form a transversely positioned'terminal, 26, on which the transversely extending terminal, 25 of the field deflector laps and to which it is pivoted by means of the pivot screw, 29. For adjusting the field deflector about this pivot to set the free end of the deflector at a greater or less distance from the magnet poles, there are struck and folded up from the bracket, 26, lugs, 30, 31, in which there is mounted rigidly a pin or rod, 32, threaded from end to end, on which there is mounted a nut, 33, knurled for manual operation, which engages a slot, 34, in the transversely projecting terminal, 25, of the deflector, 25, so that as the nut is adjusted along the screw, it carries the engaged transversely projecting terminal of the field deflector, and thereby oscillates the latter about its pivot screw. The axis produced of this ivot screw extendspast the free end of the eld deflector at the side thereof toward the rotor axis and at a distance from said free end which constitutes the lever length or radius of swing of said deflector for carrying the free end toward and from the magnet poles when it is adjusted about said pivot screw. It will be noticed that the transversely projecting terminal, 25*, of the deflector is slotted or apertured at 25* to permit the lugs, 30, 31, to project through it for carrying the threaded rod, 32, outside the transversely projecting terminal, 25*, of the deflector, so that an inner segment of the nut, 33, engages the slot, 25", in the terminal projection, 25*, of the deflector. The opposite outer segment of the nut is thereby exposed for manual engagement through an aperture, A of the case, A, for adjusting the deflector to calibrate the instrument after it is completely assembled. Preferably provision ismade for securing the parts as adjusted for calibration by providin a slot, 25, in the terminal arm, 25", of the eflector through which a set screw, 35 takes into the transverse projection, 26 of the bracket; and this screw being in the same plane transverse to the axis of the rotor as the knurled nut, may also be reached through the aper-' ture, A of the case for tightening it after y means of the nut, 33. I

In order to make the radius of swing or lever length of the deflector suflicient to prevent undue change of angle from parallelism of the face of the free end of the deflector to the sides of the magnet poles in the movement of said free end in calibration and temperature compensation, the line of bending of the terminal, 26, to project it at a right angle to the radial portion of the bracket, 25, is preferably divergent outwardly,that is, at an obtuse angle,to the radial plane in which the pivot screw, .29, is situated, thus carrying-the line of the pivot axis produced away from the free end of the field deflector, as may be seen in the modified form illustrated in Fig. 6.

In Fig. 7 there is shown a simpler but generally less desirable construction for adjusting the field deflector for calibration, consisting in providing a slot, 25"", in the transversely projected terminal, 25*, of the field deflector and setting through said slot into the transverse terminal, 26, a clamping screw, 35, which may be set to clamp the arm, 25*, against the projection, 26*, of the bracket to hold the field deflector in any position to which it maybe adjusted about the pivot screw, 29*, within the range of the slot, 25". The intended operation of the device will be obvious. The purpose being calibration andcompensation for temperature change, the adjustment of the deflector, 25, in either of the forms of the construction shown,-by means of the nut, 33, in the first form or by direct manual adjustment upon the screw, 29, in the second form,-will vary the distance of the free end of the deflector from the magnet poles and so will vary the amount of the magnetic flux which would be deflected into the path where it would be cut by the flange of the drag member, 7

I claim Y 1. In a magnetic speedometer, in combination with a casing, a rotor mounted inthe casing, a magnet device carried by the rotor for rotation in a plane containing-all the magnet poles, a drag member pivoted for oscillation aboutthe axis of the rotor; a field-deflecting member mounted upon the rotor, the means for so mounting it comprising a bracket extending from the rotor radially beyond the circumference of the magnet path of rotation, and the field deflector having its end which is free for movement positioned opposite the-inter-polar gap of the magnet, and being for movement of its free end toward and from the magnet poles, pivoted to the bracket outside said path at a point such that the pivot axis produced extends past the free end of the deflector at the side thereof toward the, rotor axis, and at a substantial distance from said free end,

and means for adjusting the deflector about its pivot to vary the distance of its free end.

from the magnet poles. V

2. In the construction defined in claim 1, the bracket having a laterally projecting terminal extending across the plane of rotation of the magnet, substantially parallel to the axis of rotation, the field deflector having a laterally projecting terminal and being-pivoted thereby to the laterally projecting bracket terminal.

3. In a magnetic speedometer, in combination with a casing, a rotor mounted in the casing, a magnet device carried by the rotor for rotation in a plane containing all the magnet poles; a drag member pivoted for oscillation about the axis of the rotor having a portion extending parallel to the magnets plane of rotation proximate thereto; a field deflecting member carried by the rotor in its rotation and having a field-deflecting part positioned at the opposite side from the magnet of said portion of the drag member; the means for mounting the field deflecting member of the rotor being a bracket arm secured to the rotor at the side thereof opposite the drag member and extending from its securement radially outward past the magnet.

4:. In the construction defined in claim 3, foregoing, said bracket being of non-magnetic material.

5. In the construction defined in claim 3, foregoing, the means of adjustment of the field deflector being a threaded part fixed on the bracket, and a nut on said threaded part, the deflector having a slot in which said nut engages for movement of the deflector thereby as the nut is adjusted along the threaded part.

6. In the construction defined in claim 3 foregoing, the bracket having a laterally projecting terminal extending across the plane of rotation of the magnet substantially parallel to the axis of rotation, the deflector having a laterally projecting terminal and being pivoted thereby to the laterally projecting terminal of the bracket, the means of adjustment being a slot in the deflector, a threaded part, fixed on the bracket, and a nut on said threaded part engaging the slot in the deflector for moving the deflector when the nut is adjusted along said part.

7. In the construction defined in claim 1, the bracket to which the deflector is pivoted being formed by bending the bracket at a right angle along a line which makes an obtuse angle with the radial plane in which the pivot of the deflector is situated, for increasing the radius swing of the free end of the deflector.

In testimony whereof, I have hereunto set my hand at Chicago, Illinois, this 11 day of October, 1920.

ANDREW C. WOOD- 

